1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine or the like, capable of performing image formation on both main and back sides of a recording sheet such as a sheet or the like.
2. Description of the Related Art
Recently, there has been an increasing demand for an image forming apparatus which forms images on both main and back sides of a recording sheet for resource saving. In this kind of image forming apparatus, a recording sheet with an image formed on one side of the recording sheet is fed again to an image forming portion under condition where the recording sheet is reversed through a switch back mechanism or the like and fed again to an image forming portion, thereby there was an image forming apparatus provided with a switch back feeding path which is used as a switch back feeding space for reversal of leading and rear ends of the recording sheet in a feeding direction and is arranged on an internal portion of a body apparatus provided with the image forming portion or on an internal portion of a peripheral apparatus to be mounted on the body apparatus later or is arranged so as to utilize a space on the outside of a setting space for the image forming apparatus. Generally, the switch back mechanism comprises a pair of rollers arranged so as to be freely rotated forward and backward at an entrance of the switch back feeding path. The pair of rollers guides the recording sheet to the switch back feeding path by normal rotation of the rollers and reverses the leading and rear ends of the recording sheet in the feeding direction by reversing the recording sheet with a part of the recording sheet keeping held between the rollers.
However, when the body apparatus or the peripheral apparatus is provided with the switch back feeding path, the configuration of the body apparatus or the peripheral apparatus becomes complicated and thereby the enlargement of the size of the body apparatus or the peripheral apparatus and increase of the related cost are caused. In addition, when the space on the outside of the location space for the image forming apparatus is utilized as the switch back feeding path, enough space should be secured in a position close to the image forming apparatus to prevent damage of the recording sheet to be switched back and fed from arising by the recording sheet's touching goods on the outside and therefore utilization of a space close to the setting position of the image forming apparatus is restricted and as a result a large setting space should be required. When this switch back feeding path is arranged on the outside of the discharging portion of the image forming apparatus, only a special post-processing apparatus provided with the mechanism which lets the recording sheet switch back and feed can be used as a post-processing apparatus to be mounted on the discharging portion later.
The applicant suggested the configuration including the switch back feeding path arranged for reversing the recording sheet in a gap formed between the body apparatus and the peripheral apparatus. By using this configuration, there is no need for the switch back feeding path on both any internal portions of the body apparatus and the peripheral apparatus and any position on the outside of the setting space for the image forming apparatus and this no need for the switch back feeding path can prevent enlargement of the size of the body apparatus or the peripheral apparatus and increase of the related cost caused by complication of the configuration of the body apparatus or the peripheral apparatus and also can prevent enlargement of the size of the setting space for the image forming apparatus and specialization of the post-processing apparatus.
However, when the body apparatus or the peripheral apparatus is brought to emergency stop and the power source is shut down because of malfunction of the control system or a recording sheet feeding jam caused by any trouble, braking force cannot be operated for the pair of rollers configuring the switch back mechanism and the pair of rollers continues to rotate under inertia force of the rollers before emergency stop of the body apparatus or the peripheral apparatus. Therefore, when the emergency stop of the body apparatus or the peripheral apparatus occurs in the middle of feeding the recording sheet under condition prior to reversing the leading and rear ends of the recording sheet in the feeding direction into the switch back feeding path by the pair of rollers rotating normally, there is a possibility that the recording sheet will continue to be moved in the feeding direction by the pair of rollers continuing to rotate normally under the inertia force of the rollers and the recording sheet will be discharged into the switch back feeding path and will not be held between the pair of rollers.
When the recording sheet is discharged into the switch back feeding path between the body apparatus and the peripheral apparatus and is not held between the pair of rollers as mentioned above, the recording sheet cannot be fed to the outside of the body apparatus and the peripheral apparatus by reverse rotation of the pair of rollers, but in the case of configuration forming the switch back feeding path in a narrow gap between the body apparatus and the peripheral apparatus, an operator's fingers cannot be put in the switch back feeding path from the outside of the body apparatus and the peripheral apparatus. Therefore, there is a problem that the recording sheet fed into the switch back feeding path cannot be removed by separating the body apparatus from the peripheral apparatus and recovery work to be performed after the emergency stop becomes complicated.